Traditionally A room thermostat simply switches the heating system on and off as necessary. It works by sensing the air temperature, switching on the heating when the air temperature falls below the thermostat setting and switching it off once this set temperature has been reached. this old typw of switch is still used today, however there is a better way !
OpenTherm (short: OT) is a standard communications protocol used in central heating systems for the communication between a central heating boiler and a thermostatic controller. As a standard, OpenTherm is independent of any single manufacturer.
Tests have shown that energy used to maintain a room at 20oC are significantly less using a modulating OpenTherm thermostat and OpenTherm boiler compared with a conventional electronic thermostat. One of the main reasons for this impressive energy saving is that an OpenTherm boiler with a modulating heating control spends longer in economic condensing mode by keeping the return temperature as low as prevailing loads permit.